Field of the Invention
This invention relates generally to devices and systems for detecting and/or verifying mechanical movements, such as verification of displacement of an output component in a mechanical device. More specifically, this invention relates to an optical motion sensor device particularly designed to monitor and verify proper operation of an infusion pump of the type used for controlled delivery of medication to a patient.
Infusion pump devices and systems are relatively well-known in the medical arts, for use in delivering or dispensing a prescribed medication such as insulin to a patient. In one form, such devices comprise a relatively compact pump housing adapted to receive a syringe carrying a prescribed medication for administration to a patient through infusion tubing and an associated catheter or the like. The infusion pump includes a small drive motor connected via a lead screw assembly for motor-driven advancement of a syringe piston plunger to administer the medication to the patient. Programmable control means are normally provided for operating the drive motor continuously or at periodic intervals to obtain a closely controlled and accurate delivery of medication over an extended time period. Such infusion pumps are utilized to administer insulin and other medications, with an exemplary pump construction being shown and described in U.S. Pat. No. 4,562,751 to Nason et al., U.S. Pat. No. 4,678,408 to Nason et al, and U.S. Pat. No. 4,685,903 to Cable et al. U.S. Pat. No. 4,562,751, U.S. Pat. No. 4,678,408, and U.S. Pat. No. 4,685,903 are hereby incorporated herein by reference.
Infusion pumps of the general type described above have provided significant advantages and benefits with respect to accurate delivery of medication over an extended time period. The infusion pump is often designed to be extremely compact and may thus be adapted to be carried by the patient, for example, by means of a belt clip or the like. As a result, important medication can be administered with precision and in an automated manner, without significant restriction on the patient's mobility or life-style.
The programmable control means for the infusion pump commonly includes internal error sensors which guard against uncontrolled, runaway delivery of medication in the event of pump failure. Accordingly, the control means is normally designed to prevent delivery of excess medication to the patient. However, infusion pumps have not included means for verifying or confirming actual mechanical displacement of the syringe plunger in response to drive signals sent by the control means to the pump drive motor. As such, prior art infusion pumps have not been able to detect mechanical pump failures which, although rare, result in undesirable nondelivery of the medication to the patient.
There exists, therefore, a significant need for improvements in medication infusion pumps, particularly with respect to providing means for monitoring and verifying actual delivery of medication to the patient in response to operation of the pump drive motor. The present invention fulfills this need and provides further related advantages.